<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Migration Class : CodeIgniter User Guide</title>

<style type='text/css' media='all'>@import url('../userguide.css');</style>
<link rel='stylesheet' type='text/css' media='all' href='../userguide.css' />

<script type="text/javascript" src="../nav/nav.js"></script>
<script type="text/javascript" src="../nav/prototype.lite.js"></script>
<script type="text/javascript" src="../nav/moo.fx.js"></script>
<script type="text/javascript" src="../nav/user_guide_menu.js"></script>

<meta http-equiv='expires' content='-1' />
<meta http-equiv= 'pragma' content='no-cache' />
<meta name='robots' content='all' />
<meta name='author' content='CodeIgniter Dev Team' />
<meta name='description' content='CodeIgniter User Guide' />

</head>
<body>

<!-- START NAVIGATION -->
<div id="nav"><div id="nav_inner"><script type="text/javascript">create_menu('../');</script></div></div>
<div id="nav2"><a name="top"></a><a href="javascript:void(0);" onclick="myHeight.toggle();"><img src="../images/nav_toggle_darker.jpg" width="154" height="43" border="0" title="Toggle Table of Contents" alt="Toggle Table of Contents" /></a></div>
<div id="masthead">
<table cellpadding="0" cellspacing="0" border="0" style="width:100%">
<tr>
<td><h1>CodeIgniter User Guide Version 2.1.4</h1></td>
<td id="breadcrumb_right"><a href="../toc.html">Table of Contents Page</a></td>
</tr>
</table>
</div>
<!-- END NAVIGATION -->


<!-- START BREADCRUMB -->
<table cellpadding="0" cellspacing="0" border="0" style="width:100%">
<tr>
<td id="breadcrumb">
<a href="http://codeigniter.com/">CodeIgniter Home</a> &nbsp;&#8250;&nbsp;
<a href="../index.html">User Guide Home</a> &nbsp;&#8250;&nbsp;
Migration Class
</td>
<td id="searchbox"><form method="get" action="http://www.google.com/search"><input type="hidden" name="as_sitesearch" id="as_sitesearch" value="codeigniter.com/user_guide/" />Search User Guide&nbsp; <input type="text" class="input" style="width:200px;" name="q" id="q" size="31" maxlength="255" value="" />&nbsp;<input type="submit" class="submit" name="sa" value="Go" /></form></td>
</tr>
</table>
<!-- END BREADCRUMB -->

<br clear="all" />


<!-- START CONTENT -->
<div id="content">


<h1>Migration Class</h1>

<p>Migrations are a convenient way for you to alter your database in a structured and organized manner. You could edit fragments of SQL by hand but you would then be responsible for telling other developers that they need to go and run them. You’d also have to keep track of which changes need to be run against the production machines next time you deploy.</p>

<p>The database table <var>migration</var> tracks which migrations have already been run so all you have to do is update your application files and call <dfn>$this->migrate->current()</dfn> to work out which migrations should be run. The current version is found in <var>config/migration.php</var>.</p>

<h2>Create a Migration</h2>

<p>This will be the first migration for a new site which has a blog. All migrations go in the folder <var>application/migrations/</var> and have names such as: <kbd>001_add_blog.php</kbd>.</p>

<pre>
defined('BASEPATH') OR exit('No direct script access allowed');

class Migration_Add_blog extends CI_Migration {

	public function up()
	{
		$this->dbforge->add_field(array(
			'blog_id' => array(
				'type' => 'INT',
				'constraint' => 5,
				'unsigned' => TRUE,
				'auto_increment' => TRUE
			),
			'blog_title' => array(
				'type' => 'VARCHAR',
				'constraint' => '100',
			),
			'blog_description' => array(
				'type' => 'TEXT',
				'null' => TRUE,
			),
		));

		$this->dbforge->create_table('blog');
	}

	public function down()
	{
		$this->dbforge->drop_table('blog');
	}
</pre>

<p>Then in <var>application/config/migration.php</var> set <dfn>$config['migration_version'] = 1;</dfn>.

<h2>Usage Example</h2>

<p>In this example some simple code is placed in <var>application/controllers/migrate.php</var> to update the schema.</p>

<pre>
$this->load->library('migration');

if ( ! $this->migration->current())
{
	show_error($this->migration->error_string());
}
</pre>


<h1>Function Reference</h1>

<h2>$this->migration->current()</h2>

<p>The current migration is whatever is set for <dfn>$config['migration_version']</dfn> in <var>application/config/migration.php</var>.</p>


<h2>$this->migration->latest()</h2>

<p>This works much the same way as current() but instead of looking for the <dfn>$config['migration_version']</dfn> the Migration class will use the very newest migration found in the filesystem.</p>

<h2>$this->migration->version()</h2>

<p>Version can be used to roll back changes or step forwards programmatically to specific versions. It works just like current but ignores <dfn>$config['migration_version']</dfn>.</p>

<pre>
$this->load->library('migration');

$this->migration->version(5);
</pre>

<h2>Migration Preferences</h2>

<p>The following is a list of all the config options for migrations.</p>


<table cellpadding="0" cellspacing="1" border="0" style="width:100%" class="tableborder">
<tr>
<th>Preference</th>
<th>Default&nbsp;Value</th>
<th>Options</th>
<th>Description</th>
</tr><tr>
<td class="td"><strong>migration_enabled</strong></td><td class="td">FALSE</td><td class="td">TRUE / FALSE</td><td class="td">Enable or disable migrations.</td>
</tr><tr>
<td class="td"><strong>migration_version</strong></td><td class="td">0</td><td class="td">None</td><td class="td">The current version your database should use.</td>
</tr><tr>
<td class="td"><strong>migration_path</strong></td><td class="td">APPPATH.'migrations/'</td><td class="td">None</td><td class="td">The path to your migrations folder.</td>
</tr>
</table>


</div>
<!-- END CONTENT -->


<div id="footer">
<p>
Previous Topic:&nbsp;&nbsp;<a href="form_validation.html">Form Validation Class</a>
&nbsp;&nbsp;&nbsp;&middot;&nbsp;&nbsp;
<a href="#top">Top of Page</a>&nbsp;&nbsp;&nbsp;&middot;&nbsp;&nbsp;
<a href="../index.html">User Guide Home</a>&nbsp;&nbsp;&nbsp;&middot;&nbsp;&nbsp;
Next Topic:&nbsp;&nbsp;<a href="table.html">HTML Table Class</a>
</p>
<p><a href="http://codeigniter.com">CodeIgniter</a> &nbsp;&middot;&nbsp; Copyright &#169; 2006 - 2012 &nbsp;&middot;&nbsp; <a href="http://ellislab.com/">EllisLab, Inc.</a></p>
</div>

</body>
</html>